This invention relates to an image stabilizer suitable for use with an image stabilizing optical apparatus provided, for example, in a video tape recorder integrated with a camera (hereinafter referred to as "video camera"). The present invention further relates to an optical axis angle variation apparatus suitable for use to realize an image stabilizer of the type mentioned and also to an optical axis angle variation mechanism suitable for use to realize an optical axis angle variation apparatus of the type mentioned.
In recent years, also for a video camera for broadcasting business use, it becomes demanded to have an image stabilizer for suppressing shaking of an imaged image caused by hand-shaking because of reduction of skilled cameramen and so forth.
In order to satisfy this demand, it has been proposed to employ an image stabilizing optical apparatus which is employed by video cameras for general consumers.
As one of image stabilizing optical apparatus employed in video cameras for general consumers, an image stabilizing optical apparatus is conventionally known. The image stabilizing optical apparatus controls a transmission light optical axis angle based on a magnitude of hand-shaking (angular displacement) of a video camera to suppress shaking of an imaged image caused by the hand-shaking. Here, the transmission light optical axis angle is an angle of an emergent side optical axis with respect to an incident side optical axis of an optical system.
In order to realize an image stabilizing optical apparatus of the type described above, an optical axis angle variation apparatus by which a transmission light optical axis angle can be corrected in accordance with a correction demand for a transmission light optical axis angle is required. Further, in order to realize the optical axis angle variation apparatus, an optical axis angle variation mechanism which can vary a transmission light optical axis angle is required.
As an optical axis angle variation mechanism of the type mentioned, a mechanism which employs a variable apex angle prism and another system which employs an optical system of the afocal type are conventionally known.
One of optical axis angle variation mechanisms of the type wherein a variable apex angle prism is employed is disclosed, for example, in Document 1 listed below. In the optical axis angle variation mechanism disclosed in Document 1, a variable apex angle prism is formed by encapsulating liquid between a pair of pivotally connected glass substrates and the angle between the glass substrates, that is, the apex angle of the variable apex angle prism, is varied to vary the transmission light optical axis angle.
Document 1: Japanese Patent Laid-Open
No. Showa 61-269572 PA1 No. Heisei 06-070220 PA1 No. Heisei 06-281889 PA1 No. Heisei 06-118471 PA1 No. Heisei 07-168235
Another optical axis angle variation mechanism of the type wherein a variable apex angle prism is employed is disclosed, for example, in Document 2 and Document 3 listed below. In the optical axis angle variation mechanism disclosed in Document 2 or 3, a plano-convex lens and a plano-concave lens having proximate spherical curvatures to each other are disposed such that spherical faces thereof are opposed to each other to form a variable apex angle prism and the two lenses are turned around the centers of the curvatures thereof to vary the angle defined by the flat surfaces of the lenses, that is, the angle of the variable apex angle prism, thereby to vary the transmission light optical axis angle.
Document 2: Japanese Patent Laid-Open
Document 3: Japanese Patent Laid-Open
As an optical axis angle variation mechanism which employs an optical system of the afocal type, an optical axis angle variation mechanism disclosed, for example, in Document 4 or Document 5 listed below is known. In the optical axis angle variation mechanism disclosed in Document 4 or 5, an optical system of the afocal type is formed from one concave lens and one convex lens, and the two lenses are moved perpendicularly to an optical axis and orthogonally to each other to vary the transmission light optical axis angle.
Document 4: Japanese Patent Laid-open
Document 5: Japanese Patent Laid-Open
However, a video camera for broadcasting business use has a large lens aperture, and a high speed responsibility is required for it. Where such an optical axis angle variation mechanism as disclosed in Document 1 is applied to a video camera for broadcasting business use, since the liquid has a considerably high viscosity, a high speed responsibility cannot be realized readily and high power dissipation is required. Further, since the video camera may possibly be used under severe conditions, there is the possibility that the liquid may leak or bubbles may be produced in the liquid by a drop of the air pressure, resulting in deterioration of the picture quality.
Meanwhile, in the optical axis angle variation mechanism disclosed in Document 2 or 3, the centers of turning movements of the two lenses are included in the optical path. While the optical axis angle variation mechanism requires a supporting mechanism for supporting the two lenses for turning motion, where it is applied to a video camera for broadcasting business use, since the video camera for broadcasting business use has a large lens aperture and has a high inertia, a large supporting mechanism and high power are required.
Further, in the optical axis angle variation mechanism disclosed in Document 4 or 5, as a supporting mechanism for supporting a lens for movement in a direction perpendicular to an optical axis, a suspension formed from a leaf spring or a like element disposed in the direction of the optical axis is employed. However, where the optical axis angle variation mechanism employs such a construction as just described, in order to support a large aperture lens, a long and large suspension is required. This gives rise to a problem that the supporting mechanism and an imaging optical system of the video camera may interfere with each other, another problem that it is difficult to assemble the support mechanism to the imaging optical system and a further problem that driving control of the suspension is difficult. Those problems arise also where a supporting mechanism which employs orthogonal slide guides are used as a supporting mechanism for a lens. Therefore, it is difficult to use the optical axis angle variation mechanism for a video camera for broadcasting business use.